ssh: fix reset{Read,Write}Thresholds for initial setup
ssh: fix reset{Read,Write}Thresholds for initial setup

Fixes a nil pointer dereference that slipped through buildbots because
it was introduced by the last two commits.

Change-Id: Ib269e910956cd8b3b46e217b03fde1b61572260a
Reviewed-on: https://go-review.googlesource.com/40530
Reviewed-by: Han-Wen Nienhuys <3269a793d567baa2fa5b041e3e5e0a5039790a2f@google.com>
Run-TryBot: Han-Wen Nienhuys <3269a793d567baa2fa5b041e3e5e0a5039790a2f@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/crypto,golang/crypto,golang/crypto,ScriptRock/crypto,ScriptRock/crypto